Let me guess. Union workers. 3 can’t work unless 3 are standing around watching them work.
Out on an oil platform, you don't get flown home at 5pm. I'm going to guess that's 3 people to cover a 24/7 operation, so there would only be one or two on duty at ant particular time. With 6 people, you could have 2 or 3 on duty 24/7 and everybody gets some rest.